"The Clubshaft is stressed by the weight of the Clubhead resisting a change in its direction or velocity – which is Acceleration. Acceleration bends the Clubshaft during Radial Acceleration (10-19-A). Change of direction bends it during Longitudinal Acceleration (10-19-C) which may be, or just include, the Clubhead Lag Pressure Point in addition to its main function of Acceleration Control."